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Ballon C.,Institute DEcologia Aquatica | Avila N.,Institute DEcologia Aquatica | Boix D.,Institute DEcologia Aquatica | Lopez-Flores R.,University of Valencia | And 4 more authors.
Limnetica | Year: 2016

Ecosystem size plays a key role in determining ecosystem functioning, affecting community stability and structure at both trophic and taxonomic levels. However, less is known about the influence of ecosystem size on environmental characteristics; for example, do larger ecosystems have higher nutrient availability? The nature of this relationship is important for gaining a better understanding of whether the effects of ecosystem size on community functioning are direct or indirect. Indirect effects may exist when the environmental characteristics of larger ecosystems are different from those of smaller ones, and thus the different functioning of communities observed along the ecosystem-size gradient may respond to, for instance, different levels of nutrient availability, and not uniquely to different ecosystemsizes. Here,we tested whether the environmental characteristics (i.e., the physical, chemical and biological characteristics) of temporary ponds of various sizes differed. We chose temporary ponds because they are abiotic controlled systems in which abiotic factors have a strong influence on aquatic communities. However, temporary ponds are usually spatially clustered; consequently, pond locality might also be important in determining the environmental characteristics of a pond (i.e., ponds close to one anothermay share similar features).We therefore examined whether pond locality is a more important factor than size in determining the environmental characteristics of a pond. To do so, we sampled environmental characteristics (chlorophyll-A, nutrient concentrations, macrophyte biomass, water temperature, conductivity, pH, dissolved oxygen, and total organic and inorganic carbon) of ponds in 5 different localities. A cluster of ponds (10 to 12) was sampled in each locality. Ponds encompassing a wide range of sizes were selected for sampling within each locality. We also performed a meta-Analysis (including data from 27 temporary pond localities) to investigate whether the environmental characteristics of the ponds sampled in this study were representative of Mediterranean temporary ponds, and thus if such characteristics could be used to distinguish between Mediterranean temporary ponds from temporary ponds located outside of the Mediterranean region. Our results showed that locality had a strong effect on the environmental characteristics of temporary ponds, whereas size had only a weak influence; only chlorophyll-A and pond depth showed a robust relationship with size, as both increased with pond size independently of locality. Moreover, our results suggest that the typology of the temporary pond (i.e., if they were mountain temporary ponds, salt marsh ponds or lowland ponds) had a larger influence on several environmental characteristics than did regional location (i.e., Mediterranean). © 2016 Asociación Ibérica de Limnología, Madrid. Spain.


Morin S.,IRSTEA | Morin S.,Institute dEcologia Aquatica | Proia L.,Institute dEcologia Aquatica | Ricart M.,Institute dEcologia Aquatica | And 7 more authors.
Vie et Milieu | Year: 2010

We studied the adverse effects of triclosan, a widely used biocide commonly reported in surface waters, on the structure and function of benthic diatom communities. Laboratory-grown biofilms were exposed (i) to chronic contamination by increasing concentrations of triclosan and (ii) to a short-pulse of sublethal triclosan concentrations followed by a 2-week recuperation period. The first experiment was performed using 6 nominal concentrations ranging from 0.05 to 500 μg/L triclosan to obtain the concentration - effect relationships for benthic diatom communities. Here effects at the highest triclosan concentration in the diatom community consisted of a 63 % increase in diatom mortality, with respect to control conditions. The second experiment aimed at determining the long-term effects of the toxicant and biofilm recuperation after addition of 60 μg/L triclosan for 48 h exposure. After two weeks the sublethal pulse had caused a decrease in diatom growth rates and a significant delay in the exponential phase of growth. The triclosan pulse provoked a decrease in diatom species richness and diversity. The diatom communities were dominated by six species, with Achnanthidium minutissimum being highly preponderant, and variations were not large enough to provide information about sensitivities/tolerance to triclosan in different species.

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